Common X-ray tubes generate X-rays by hitting electrons against a metal anode target with high energy. For example, an x-ray tube uses a principle of generating Bremstralung x-rays or specific x-rays generated, depending on the substance of the anode target. The electron source that emits electrons is usually a thermal electron source.
Meanwhile, there is an x-ray tube emitting electrons by using nano-substances. The x-ray tube uses a field emitter. It is important in the x-ray tube using a field emitter to apply nano-substances, which are effective for field emission, to a cathode electrode, to form a gate electrode to apply an electric field to the nano-substance, and to seal the structure of the x-ray tube under vacuum.
However, the x-ray tube using a field emitter is necessarily equipped with various electrodes such as a gate electrode, an emitter electrode, an anode electrode and a cathode electrode. There is a problem in that it is difficult to reduce the size because the size of the x-ray tube is increased by various electrodes.